Refuse collection trucks are generally used for collection of trash and other refuse or recyclables. Typically, a refuse collection truck has a body which is supported by a chassis and wheels and which stores the refuse for transport. Rear loading refuse trucks also include a tailgate assembly mounted at the back-end portion of the truck. This tailgate assembly has a hopper for receiving refuse and an opening between the hopper and the body for transporting the refuse to the body. Typically, the tailgate assembly has a sweeping mechanism for pushing and compacting the refuse in the hopper before the packing mechanism forces the refuse into the body or storage area of the refuse collection truck. The packing and sweeping mechanisms work together as the compactor by forcing the fresh refuse against the old refuse into the body, thereby compacting the refuse within the body to a maximum density.
In general, it is necessary for the packing/sweeping mechanisms of this type of packer to have four travel paths. This is generally accomplished by having a packing panel which is pivotally attached to a carrier panel. The first and second paths accommodate the addition of fresh refuse into the hopper. From a position where the packer blade is holding the refuse in the body, the first path is having the packing blade rotate rearwardly up and over refuse piled in the hopper. This is called the unsweep cycle. The second path moves the carrier panel and packing blade down such that the blade is in a position above and behind the refuse. This is called the unpack cycle. The third part of the path is when the packing panel rotates toward the front of the truck. This is generally called the sweep motion as it sweeps material out of the rear of the hopper toward the front. The fourth portion is called the packing cycle. In this portion, material is moved up from its position in the bottom of the hopper to be packed into the body of the truck.
The object of the first two paths is to get the blade up and over the refuse in such a way as to not push the refuse back into the street and to allow the refuse to be built up as high in the hopper as possible. When the packing/sweeping mechanisms are in the packing mode or have stopped at the end of the packing mode, the packing/sweeping mechanisms are positioned to allow refuse into the hopper without obstruction. As the packing/sweeping mechanisms return to the contain mode, at the end of the pack cycle, they hold the refuse in the body and pack it against old refuse. As more and more material is packed into the body, the ejector panel gradually moves toward the front of the body until the body is full.
The hopper of the tailgate assembly is designed to receive refuse containers of varying sizes which are either hand-load operated or lift-mechanism operated. The hand-loading operation requires a refuse crew to collect the refuse in-hand and put it into the hopper of the refuse collection truck. The lift-mechanism operation uses a device to grab the refuse container, raise the container above the rear opening of the hopper and tilt the container sufficiently to dump all the refuse into the hopper.
The prior art rear loading types of packers that have an upper panel connected to a lower panel use several ways to control the movement of the panels. The first method is to have the upper panel slide in a groove and the lower panel rotates at its end controlled by a hydraulic cylinder connected between the two panels. Another method uses two sets of two forward projecting links connected at one of their ends to the tailgate and connected at their other ends to the upper panel. A typical representation of this method is shown in U.S. Pat. No. 3,999,669. This four-bar mechanism controls the motion of the upper panel. The lower panel rotates at its end controlled by a hydraulic cylinder connected between the two panels. Yet another method uses two sets of two rearward facing links connected at one of their ends to the tailgate and connected at their other ends to the upper panel. This four-bar mechanism controls the motion of the upper panel. The cylinder that controls the lower panel is connected between the tailgate and the lower panel. A representative example of this is shown in U.S. Pat. No. 5,478,188. Yet another method used to control the panels is to rotatably connect the upper panel to the tailgate on a single axis such that it can swing. The prior art attached the cylinder for moving the lower panel between the tailgate and the lower panel. A representative example of this is shown in U.S. Pat. No. 4,460,307.
The efficiency of a packer is based on the amount of refuse the packer can pack in what amount of time. Therefore, the swept volume and the cycle time are integral parts of the equation and should be optimized. The number of cycles or frequency of operation of the packing/sweeping mechanisms depends upon the capacity of the hopper. A large hopper can temporarily store a larger volume of refuse and accordingly, less time is lost while waiting for the packing/sweeping mechanisms to complete their cycle. The height of the sill at the tailgate opening is one factor that limits hopper capacity. The higher the refuse receiving opening is above the ground, the more effort is required by the workmen in dumping their containers into the hopper. Accordingly, the sill over which the refuse is dumped into the hopper should be as low as possible. In general it is desirable to have as light a collection vehicle as possible. It is desirable to have the overhang past the rear axle as short as possible. It is desirable to have as high a density packing as feasible. It is desirable to have the cycle time as quick as possible, especially the time from packing to being able to reload the hopper. There are also restrictions on height and width that must be maintained. There is also a minimum exit angle from the rear tires to the bottom of the hopper that should be maintained for ground clearance. It is also desirable to have a packer that has low maintenance and is inexpensive to build.
The prior art packers that use a slot to control the motion of the upper panel have the following deficiencies. The straight motion during the pack cycle means that the hopper floor will be flat in that area. Flat floors require additional stiffeners to support the pressure on them, thus increasing the weight of the tailgate. Slides are difficult to seal and therefore are prone to deteriorate more quickly than pivot style of bearings. Slides are also more difficult to support structurally than a single pivot, thus requiring more material and weight to do so. Also, the straight path during the packing cycle limits the hopper capacity somewhat. The blade tip must travel from the lowest point at the end of the sweep up to the hopper lip. If this path is curved there is more usable hopper volume than if it is straight.
The prior art that utilizes forward facing links has the following deficiencies. The amount of bearings to make this work is large. This again makes support of the bearings more difficult, adding weight. More bearings result in more maintenance problems. This method also has a hopper that has a major change of direction between the sweep and pack cycles. This wears the hopper out more quickly. This discontinuity also causes more problems with moving incompressible objects into the body and fall back is a greater problem. This prior art also uses a packing cylinder in the pull mode verses the push mode. This means that it does not make as good use of the available force as possible.
The prior art that utilizes rearward facing links has the following deficiencies. The amount of bearings to make this work is large. This again makes support of the bearings more difficult, adding weight. More bearings result in more maintenance problem, not only for the bearings themselves, but for the maintenance of parts they connect. This prior art also uses a packing cylinder in the pull mode verses the push mode. This means that it does not make as good use of the available force as possible.
The prior art that uses a swinging type of attachment for the upper panel is configured such that the motion of the panels on the unpack stroke tend to push material out of the hopper. The packer cylinders are pulling to pack and thus do not have the added force for the same pressure that pushing would give. In addition, high pressure is needed during the sweep and pack cycles. Cylinders that are pulling during the high pressure cycle are more likely to leak hydraulic fluid than those that push. The angle of incidence of the tip of the panel to the hopper is far from 90 degrees. This gives a tendency for the blade to ride up over the material in the hopper giving larger pressures in the cylinders.
Therefore, it would be highly advantageous to remedy the foregoing and other deficiencies inherent in the prior art.